The gates of Paradise Dam at Bundaberg will be opened in the coming days to allow for repairs after January's record flood.
SunWater will dramatically lower the level of water in the dam and says about 23,000 megalitres per day will be released over a four to five day period.
The dam has been spilling since the flood and some downstream residents are still isolated by the high levels in the Burnett River.
The repairs are expected to cost about $2 million, but Bundaberg Mayor Mal Forman says he has been assured the dam is safe.
"There is no risk," Councillor Forman said.
"We're advised there is not a problem with the integrity of the dam ... and the chance of more damage occurring is very, very small."
SunWater chief executive Peter Boettcher says the floods damaged the dam's spillway dissipater - the concrete slab downstream of the dam.
"As the river flows have subsided staff have been able to undertake closer inspection of the dam and have identified that the damage is scouring of the dissipaters," he said.
"Our first action will be to stop the dam from overflowing to enable safe access for the repairs to be carried out."
Councillor Forman says the work is necessary but will prolong the inconvenience for residents still isolated by the swollen Burnett River.
"In the low-lying areas there are some roads that will have some flooding," he said.
"Those roads are already flooded now with the natural flow of water that's happening at the moment."
Councillor Forman says there is already about 16,000 megalitres a day spilling from the dam.
"These additional releases won't cause any more damage, they will just mean the water stays up for longer," he said.
The repair works will require the construction of a temporary access road across the river bed.
Rock anchors and concrete will then be installed at the base of the dam to repair the damage.
SunWater says the work will start mid to late next week and will take two to three weeks to complete.
© ABC 2013
18:16 EST Heavy rain has stranded about 40 people at William Creek in the South Australian outback due to flooded roads and low cloud has grounded aircraft.